bola = 'bola.gif'
campo = 'campo.jpg'

import pygame, sys
from pygame.locals import *

pygame.init()

screen=pygame.display.set_mode((620,390),0,0)

background=pygame.image.load(campo).convert()
mouse_c=pygame.image.load(bola).convert_alpha()
j = "teste"
while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    screen.blit(background, (0,0))

    x,y = pygame.mouse.get_pos()
    x -= mouse_c.get_width()/2
    y -= mouse_c.get_height()/2

    screen.blit(mouse_c,(x,y))

    pygame.display.update()
